A centrifugal separator of this kind is described in DE 37 14 627. The centrifugal rotor in this case is supported at the top of the vertical spindle, and the driving device comprises an electric standard type motor, which may be arranged in two different ways.
According to a main alternative the electric motor is situated below said second bearing, as shown in the drawing. Also another alternative is suggested, in which the electric standard type motor would be arranged between said two bearings. An arrangement according to the last-mentioned alternative would have the advantage that the whole centrifugal separator became more compact.
As can be seen from DE 37 14 327 said second (lower) bearing is radially immovable in relation to the frame, whereas said first (upper) bearing may move somewhat radially, so that the spindle may adapt itself to changes of position of the centre of gravity of the centrifugal rotor, which occur during operation of the centrifugal rotor. Such changes of position always occur to a larger or smaller extent and are caused by unbalance of the centrifugal rotor. Thus, the spindle will always perform oscillatory motions.
An arrangement of an electric standard type motor between the two layers, in accordance with the proposal in DE 37 14 627, for obtainment of a more compact centrifugal separator would, however, bring the disadvantage that the motor were forced to follow said oscillatory motions of the spindle. This would lead to an increased load on both the bearings and the frame, and particularly in connection with large and heavy centrifugal rotors having correspondingly large and heavy driving motors, this could become an unacceptable problem.
The object of the present invention is to provide a driving device for a centrifugal separator of the above defined kind, which driving device does not cause the bearings and the housing being subjected to unacceptably heavy loads but, despite this, makes possible a compact construction for the whole centrifugal separator.